QFAE-nB alleviates pulmonary fibrosis by inhibiting the STING pathway in mice

Pulmonary fibrosis (PF) is an irreversible lung disease that severely affects human respiratory function. Traditionally, the natural plant Quzhou Fructus Arantii (QFA) has therapeutic effects on respiratory diseases. However, the effects and the mechanism of anti-fibrotic have not been elucidated. In this study, QFAE-nB was extracted from QFA, the aims of this study include understanding the correlation between Bleomycin (BLM)-induced PF and STING pathway in mice, as well as exploring the role and mechanisms of QFAE-nB in the treatment of PF. QFAE-nB was extracted from QFA, six main chemical components in QFAE-nB were identified by HPLC–QTOF–MS/MS, and quantitative analysis was conducted by HPLC. qPCR and Western blot were used to verify the molecular mechanism of QFAE-nB, and the anti-fibrotic effect of QFAE-nB was determined by hematoxylin-eosin (HE) staining and Masson staining as well as immunohistochemistry. TREX1-KO and STING-KO mice were used to verify the relationship between STING and PF and the important target action of QFAE-nB. Six main flavonoids in QFAE-nB were identified as eriocitrin (0.76%), neoeriocitrin (2.79%), narirutin (4.31%), naringin (35.41%), hesperidin (1.74%), and neohesperidin (27.18%). The results showed that BLM-induced PF was associated with its exacerbated release of proinflammatory factors and chemokines in lung tissues. In addition, QFAE-nB alleviated BLM-induced lung fibrosis in mice by inhibiting the activation of the STING signaling pathway and reducing the signal transduction of TBK1–IRF3 and TBK1–NF-κB pathways. Notably, knockout of the TREX1 gene caused massive inflammation and even induced PF in the lung tissues, whereas QFAE-nB effectively alleviated inflammation and reduced PF. The deletion of the STING gene suppressed BLM-induced PF and inflammation, but STING-KO mice treated with QFAE-nB showed even lower expression levels of proinflammatory factors and chemokine. The STING pathway plays an important role in PF, and QFAE-nB alleviates PF by mainly targeting the inhibition of the STING pathway to reduce inflammation. Together, the study paves the way for targeting the STING pathway in PF treatment.